1. Technical Field
The present invention relates to a white light-emitting diode (LED) structure and, more particularly, to a blue light leakage-suppressing LED structure in which a thermochromics material can change its hue as the temperature of the LED is changed.
2. Description of Related Art
Driven by the rising awareness of environmental protection and the expectation of sustainable development, energy-saving light sources are now in extensive use. In particular, the demand for LEDs, which feature very low power consumption and adequate brightness, has increased the most.
The estimated service lives of LEDs are generally specified with an L70 value, which indicates the time for which the luminous flux of an LED is expected to last before dropping to 70% of that which has been achieved under a thermally stable condition. Once an LED reaches the L70 threshold, its temperature (or more particularly the junction temperature inside the LED) will be approximately equal to or higher than 150° C., and the correlated color temperature (CCT) of the LED at this moment will be about 9000 K or above.
However, during the period in which a white LED is about to reach but has not reached the L70 threshold, the light emission efficiency of the white LED is already lowered by the heat generated, and the lowered light emission efficiency results in more. heat. Eventually, the absorption efficiency of the fluorescent material in the white LED will be reduced, leading to a significant leakage of blue light.
More and more researches spurred by the increasing popularity of LEDs have shown that blue light is highly detrimental to the structure of the human eye. The eyes may be injured beyond repair if exposed to blue light for an extended period of time.
In view of this, and in order to bring about substantial improvement in people's quality of life, the LED industry, if not the entire lighting industry, has made great efforts in developing a simple yet effective technology or LED structure that enables a portion of a white LED to effect a change in hue before the white LED generates a large amount of heat and emits excessive blue light. The change in hue is intended to prevent unnecessary injury otherwise attributable to a significant leakage of blue light and, by reducing the brightness of the white LED considerably, to remind the user that the light source needs to be replaced.